The present invention relates to a system and method for plasma-assisted processing of microelectronic devices, and, more particularly, to a method, apparatus, and system for performing high-performance inductively-coupled plasma ionized physical-vapor deposition of thin films, such as those which are widely used in manufacturing of semiconductor integrated circuits, data storage thin-film heads, flat-panel displays, photovoltaic devices, and other devices used in electronics and information systems. Applications of particular interest include integrated circuit metallization as well as collimated deposition of thin films for fabrication of thin-film heads.
Plasma-assisted physical-vapor deposition (PVD) is a commonly used thin-film fabrication technology for manufacturing of semiconductor, data storage, flat-panel display, and photovoltaic devices. PVD processes are widely used in advanced metallization applications for deposition of interconnect liner/barrier layers and interconnect metal lead layers in semiconductor chips. For instance, PVD processes are utilized to deposit Ti/TiN liner/barrier layers as well as metallization materials such as Al or Cu. Plasma sputtering is the most important PVD fabrication technique.
Existing commercial PVD technologies usually employ DC or RF magnetron sputtering in vacuum chambers. Typical commercial PVD equipment includes a single-substrate (single-wafer) vacuum process chamber (preferably designed as a cluster tool module), a temperature-controlled chuck (with the option to apply electrical bias power to the chuck) to hold the substrate, and a sputter target (or magnetron cathode) that contains the desired material. DC magnetron plasma excitation (with DC power levels up to 10 kW to 20 kW) is usually used for sputter deposition of electrically conductive materials such as Al, Ti, Co, and TiN. RF magnetron or pulsed DC (AC) sputtering is usually used for sputter deposition of electrically insulating (or resistive) materials. RF diode sputtering (as opposed to magnetron PVD sputtering) is the preferred choice for sputter deposition of some magnetic materials and insulating materials for applications such as thin-film head fabrication.
Each of these PVD methods generates a plasma from an inert gas such as Ar or another reactive gas such as nitrogen and sustains the plasma near the target area. The target material atoms or molecules are then sputtered from the target surface and deposited on the device substrate. Sputtering of the target occurs due to the impact of energetic argon ion species. During the sputtering process, the sputtered species (mostly neutrals) are emitted within the vacuum chamber plasma environment over a wide range of spatial angles and a portion of the sputtered flux deposits on the device substrate. Other sputtering processes, such as reactive sputtering processes, use nitrogen or oxygen or another reactive gas usually mixed with an inert gas such as argon within the vacuum chamber. Reactive magnetron sputtering processes that deposit TiN layers from elemental Ti targets illustrate an example of this technique.
In general, the flux of the sputter atoms or species that the PVD target material emits has a relatively broad angular distribution. Thus, some of the sputtered flux is further scattered by the collisions with the sputtering gas atoms. The sputter flux of species arriving at the substrate surface has a relatively broad distribution angle. This broad distribution angle does not present a problem in applications involving substrates without high aspect ratio features or with relatively minor surface topography features.
However, most semiconductor device manufacturing applications involve substrates with high-aspect-ratio features. These applications require some degree of spatial filtering or collimation for the sputter species. A broad angular distribution of the PVD flux provides poor collimation or a low degree of collimation, whereas a narrow angular distribution relative to the perpendicular axis indicates a higher degree of PVD collimation. For instance, semiconductor interconnect applications require collimated sputtering for deposition of the contact and via liner/glue and barrier layers (e.g. Ti/TiN) when using high aspect ratio (for instance, on the order of xe2x89xa73:1) contacts and vias due to the bottom coverage and sidewall coverage requirements. For a contact/via hole of width (or diameter) W and height H, the following parameters can be defined:
A.R. xcex94  H  W
(aspect ratio)
Bottom Coverage xcex94      t    b    d
Sidewall Coverage xcex94      t    s    d
(step coverage)
where d is the thickness of sputtered material layer on extended flat top surfaces (also known as the field area), tb is the sputtered material thickness at the bottom of the hole, and ts is the thickness of the sputtered material on the hole sidewall at mid height.
In conventional PVD processes without any built-in sputtering collimation feature, the bottom coverage and sidewall coverage of the sputter deposited material degrades significantly as the microstructure aspect ratio increases. This degradation becomes increasingly and rapidly worse for microstructure aspect ratios of greater than 3:1. As a result, for applications requiring good bottom coverage (e.g., xe2x89xa725%) and sidewall coverage (xe2x89xa750%), existing PVD technologies use one or another of the various existing methods of PVD collimation. These include physical collimation, natural or long-throw collimation, hollow-cathode PVD collimation, and inductively-coupled plasma (ICP) enhanced ionized PVD collimation. For example, FIG. 1a (prior art) shows a typical physical collimation technique. A collimator plate is placed between the PVD target or cathode assembly and the substrate inside the vacuum chamber. The collimator plate, usually made of aluminum or titanium, consists of an array of circular or hexagonal (honeycomb) closely packed holes (see FIG. 1(b)) that typically have an aspect ratio of 1:1 or higher. The collimator plate operates as a spatial filter to reduce the angular distribution of the sputter flux species arriving at the substrate.
Of the existing PVD collimation methods, ICP PVD collimation may provide the greatest degree of collimation control, including real-time adjustability, the greatest deposition rate for a given degree of collimation, and the least amount of maintenance downtime to clean PVD chamber components. However, despite these advantages, existing ICP PVD collimation methods have a number of drawbacks and disadvantages.
First, existing ICP PVD processes do not allow for variable (adjustable in real time) antenna position relative to the target and substrate. As a result, variations in the target material properties and other aspects affecting process uniformity (such as ionization uniformity and ionization intensity near the wafer, which affect degree of collimation and deposition rate) cannot be compensated for by repositioning the antenna during the PVD process itself, but instead require equipment downtime to change the position of the antenna relative to the substrate and target. The need to manually reposition the antenna to improve process uniformity has a negative impact on the overall equipment uptime and product throughput, resulting in increased process expense.
Second, the ICP antenna is exposed to the PVD plasma, resulting in etching and sputtering of the antenna. The antenna must preferably therefore be made of the same material as the target since the antenna material itself will be sputtered and deposited throughout the process chamber, including on the substrate. The antenna is in essence also the target deposition material and is consumed, requiring frequent replacement. The need to replace the ICP antenna likewise negatively impacts overall equipment uptime and product throughput and results in increased cost due to replacement of antennas, and limits the materials that can be deposited unless the material can be fabricated as an antenna.
Third, current ICP PVD processes use a single-zone antenna to couple additional energy to the plasma and thereby further ionize the species atoms coming from the target. Use of a single-zone antenna does not allow real-time individualized control of the ionization and collimation in distinct areas of the process environment. Process and collimation uniformity are therefore not optimized over the entire substrate surface.
Therefore, there is a need for an ICP PVD collimation technique that provides the capability for real time adjustment of ICP PVD antenna position relative to the target and substrate.
A further need exists for an improved ICP PVD collimation technology that does not consume the ICP PVD antenna and therefore does not require the ICP PVD antenna to be made of the same material as the target.
A still further need exists for an ICP PVD technology with the capability of using a multi-zone ICP PVD antenna to allow for real-time independent control of the ionization and collimation in distinct areas of the process environment.
The present invention provides an apparatus and method for processing a substrate such as a semiconductor wafer using inductively-coupled plasma (ICP) enhanced ionized physical-vapor deposition (PVD) (particularly plasma sputtering) that substantially eliminates or reduces disadvantages and problems associated with previously developed PVD techniques for deposition of various material layers.
In particular, the present invention provides a system and method for performing an inductively-coupled plasma ionized physical-vapor deposition process for depositing a material layer onto a work piece such as a silicon substrate. The system includes a PVD process chamber within which are contained a target/cathode assembly, a chuck assembly, a process medium, an adjustable-height inductively-coupled ionization coil segment and an antenna actuator for controlling the relative vertical position of the variable-height inductively-coupled ionization coil segment. The variable-height inductively-coupled ionization coil segment can be contained within a dielectric liner and can be substantially covered by a multi-slotted electrostatic shield. The variable-height inductively-coupled ionization coil segment can be comprised of one or more coil loops electrically interconnected to form one or more zones which are powered by one or more radio-frequency power supplies through at least one adjustable passive electrical component for providing multiple inductive-zone operation during a deposition process. The chuck assembly can be an adjustable-height chuck assembly further comprised of a chuck actuator connected to the chuck assembly for controlling the relative vertical position of the chuck assembly with respect to the target/cathode.
A second embodiment of the improved PVD apparatus of this invention includes an antenna coil contained within a dielectric housing integrated into either the variable-height chuck assembly of the first embodiment or into a clamp table on the variable-height chuck assembly. Still a third embodiment of the improved PVD apparatus of this invention further comprises an inductive antenna tubing contained within a dielectric lid-lift insert between the lid and the main chamber wall of the vacuum process chamber.
The present invention provides an important technical advantage of an ICP PVD collimation technique that has the capability for real time adjustment of ICP PVD antenna position relative to the target and substrate.
Another technical advantage of the present invention is that it provides an improved ICP PVD collimation technology that does not consume the ICP PVD antenna and therefore does not require frequent replacement of the ICP PVD antenna, or that the ICP PVD antenna be made of the same material as the target.
A further technical advantage of the present invention is the capability of using a multi-zone ICP PVD antenna to allow for real-time individualized control of the ionization and collimation in distinct areas of the process environment.